Insufficient cooling is the reason. TEC's rated at 80W DRAW 80W, but don't provide 80W or cooling potential. I think, depending on voltage and the actual TEC used, that most TECs are about 70% efficient. Even then, that is under ideal conditions, so it makes sense to aim way high. If you are going to be cooling a CPU, I wouldn't bother with anything less than a good 172 watter. And if you are going to get a TEC watercooling setup and PSU, you might as well get a 226W.
Also, most modern CPU's dissipate ~100W, so an 80W TEC would fail, even if it was 100% efficient.
BO(V)BZ
|